OGeek|极客世界-中国程序员成长平台

标题: ios - NSFetchResultsController 的 NSPredicate [打印本页]

---

作者: 菜鸟教程小白    时间: 2022-12-12 21:52
标题: ios - NSFetchResultsController 的 NSPredicate

我正在尝试为我在 UITableView 中使用的 NSFetchResultsController 创建一个 NSPredicate。 我有 3 个实体，User(一对多)-> Visit(一对多)-> Treatment，并希望获得所有用户接受的治疗。

我尝试过使用子查询、SELF、ANY，并且只返回 Visits 而不是 Treatments。

有人可以指导我如何从用户实体访问治疗实体吗？

提前感谢您的帮助!

Image of the CoreData Model

编辑

这是我目前用来尝试获取治疗的代码

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:kTreatmentVisits];
fetchRequest.sortDescriptors = descriptors;
fetchRequest.fetchBatchSize = 10;
fetchRequest.predicate = [NSPredicate predicateWithFormat"ANY treatmentVisits = %@.visitTreatment", user.userVisit];

结果我得到的是访问，而不是治疗

<NSFetchRequest: 0x60b000148a40> (entity: treatmentVisits; predicate: (ANY treatmentVisits == {<Visits: 0x60b0000a0ad0> (entity: VisitsEntity; id: 0xd0000000000c000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p3> ; data: {
visitCause = "";
visitEndDate = nil;
visitId = nil;
visitRecommendation = "";
visitStartDate = "2016-08-11 04:43:50 +0000";
visitTreatment = "<relationship fault: 0x60300025e6d0 'visitTreatment'>";
visitType = 0;
visitUser = "0xd000000001940000 <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/UsersEntity/p101>";
}), <Visits: 0x60b0000bec10> (entity: VisitsEntity; id: 0xd00000000008000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p2> ; data: {
visitCause = "";
visitEndDate = nil;
visitId = nil;
visitRecommendation = "";
visitStartDate = "2016-08-04 20:26:33 +0000";
visitTreatment = "<relationship fault: 0x60300025e850 'visitTreatment'>";
visitType = 0;
visitUser = "0xd000000001940000 <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/UsersEntity/p101>";
}), <Visits: 0x60b000148570> (entity: VisitsEntity; id: 0xd00000000010000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p4> ; data: <fault>), <Visits: 0x60b000148620> (entity: VisitsEntity; id: 0xd00000000004000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p1> ; data: <fault>)}.visitTreatment); sortDescriptors: ((
"(treatmentStartTime, descending, compare"
)); batch size: 10; type: NSManagedObjectResultType; )

我希望能够访问 visitTreatment

中的内容

我也试过

fetchRequest.predicate = [NSPredicate predicateWithFormat"SELF IN %@", user.userVisit];

结果相同。

---

Best Answer-推荐答案

首先，如果您想获取治疗，您的 FRC 的基础提取必须指定治疗实体:

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName"TreatmentsEntity"];

然后通过指定谓词将结果限制为给定 UsersEntity 的处理，例如 requiredUser:

fetchRequest.predicate = [NSPredicate predicateWithFormat:"treatmentVisits.visitUser == %@", requiredUser];

然后您需要直接执行获取请求:

NSError *error = nil;
NSArray *results = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (results == nil) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();    
} else {
    NSLog(@"Results is %@",results);
}

或者，对于获取的结果 Controller ，您使用 fetchRequest 初始化 FRC，然后调用 performFetch:

NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
NSError *error = nil;
if (![frc performFetch:&error]) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
} else {
    NSLog(@"Results %@",frc.fetchedObjects);
}

关于ios - NSFetchResultsController 的 NSPredicate，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/39173965/

---

欢迎光临 OGeek|极客世界-中国程序员成长平台 (http://sqlite.in/)

Powered by Discuz! X3.4